Mosquito-transmitted diseases are a major cause of suffering and death in the tropical world. Malaria, alone, kills one to two million people every year. The urgency for developing new control strategies is underscored by the development of resistance by parasites to previously effective drugs, by the resistance of mosquitoes to a variety of insecticides, and by the lack of an effective vaccine. Inhibition of the parasite's life cycle in the mosquito is a strategy that has not yet been explored. This proposal focuses on the gut of the human malaria vector Anopheles gambiae. The gut is the first site of interaction between the mosquito and the parasites it transmits. Ingestion of blood by the adult mosquito triggers the secretion of a type 1 peritrophic matrix (PM1), which is a thick extra- cellular sheath that completely surrounds the blood meal and any ingested parasites. During larval stages, the mosquito secretes a completely different type 2 peritrophic matrix (PM2), which is thin and synthesized constitutively. No insect PM has yet been characterized molecularly and PM function remains speculative. However, it is clear that the PM1 poses a partial barrier for malaria parasite invasion. Major objectives of this proposal are to molecularly characterize genes encoding PM1 and PM2 proteins, and to explore the use of PM1 genetic regulatory elements to develop novel malaria transmission control strategies. Specifically, adult PM1 genes will be cloned based on amino acid sequence information of fractionated proteins. The genes will be characterized by DNA sequencing, RNA blot analysis and in situ hybridization experiments. Antibodies to recombinant PM1 proteins will be used to determine if PM1 proteins are stored in secretion vesicles. Genes encoding larval PM2 proteins will be cloned by use of a subtractive library created by a polymerase chain reaction-based method. The PM2 genes will be characterized by methods similar to those used for the PM1 genes. The potential use of regulatory elements from PM1 genes for blood- induced release of anti-parasite substances into the mosquito gut will be assessed by a newly developed approach that relies on infection of mosquitoes with a retroviral vector. Genetic transformation of mosquitoes is likely to become available in the near future. The proposed experiments will lead to a better understanding of PM structure and function and may ultimately lead to the production of transformed mosquitoes with reduced competence for disease transmission.